What a fiber-using function would look like if you called `done` rather than letting the fiber do it for you. Compare https://gist.github.com/wearhere/4f07d298d077da9dcb2d. More info at https://www.mixmax.com/blog/node-fibers-using-synchronize-js.

calling-done-manually.js

function processFile(fileName, done) {
  sync.fiber(function() {
    var data;
    try {
      data = /* first `sync` call */;
    } catch(e) {
      done(e);
      return;
    }

    var processedData;
    try {
      processedData = /* second `sync` call */;
      done(null, processedData);
    } catch(e) {
      done(e);
    }
  });
}